The hocks---easily bumped and jostled---are particularly injury-prone parts of a horse's anatomy. In most cases, hock injuries that cause the build-up of tarsal synovial fluid are easily detectable and treatable and will not lead to long-term conditions.
Overview of Hock Injuries
Fluid build-up in the hocks is often caused by a bog spavin or bursitis of the hock---commonly known as capped hock. Both are easily treated if detected early, but they tend to recur unless preventive measures are taken.
Identifying a Bog Spavin
Bog spavins are most often the result of weak hocks, but any trauma to the hock area may cause them. A bog spavin produces a noticeable, soft swelling on the inside of the hock. If you manipulate the swollen area, you may feel the fluid move.
Treating a Bone Spavin
Lameness in conjunction with a bog spavin may indicate osteocondritis, a disease that most often affects fast-growing horses. It requires immediate veterinary care. When no lameness is apparent, careful exercise may reduce swelling. Attention to proper shodding is essential. If swelling persists, a veterinarian may choose to drain the fluid or prescribe medication to reduce swelling and improve hock health.
Identifying a Capped Hock
Trauma to the hock area is the most common cause of a capped hock, which produces a lemon-size, soft swelling on the tip of the hock. Pain may develop over time.
Treating a Capped Hock
A capped hock requires immediate veterinary care to prevent swelling from forming a permanent subcutaneous bursa. A veterinarian may drain the fluid and prescribe rest, a series of cortisone injections, or other anti-inflammatory measures.
Either condition---a bone spavin or capped hock---should prompt an inspection of the horse's living quarters to identify potential dangers.